This invention pertains to a refrigeration apparatus having a flooded evaporator, and more particularly to lubricants with decreased solubility and fluorocarbon refrigerants and increased foaming characteristics.
In refrigeration systems with an oil lubricated compressor and a flooded evaporator, oil from the sump of a compressor can migrate to a flooded evaporator under certain low load operating conditions. Lubricant return to the compressor can be inadequate if the lubricant does not entrain with the refrigerant gas passing through the evaporator. Oil return problems occur when oil remains dissolved in the refrigerant.
Lubricant return problems have been experienced particularly in water chillers having a screw compressor with a flooded evaporator. Oil injected into the working chamber of a screw compressor, is atomized and becomes entrained in the refrigerant gas undergoing compression. Oil separators can be used in such systems to remove most of the oil that is entrained in the refrigerant gas as it leaves the compressor. However, as much as 10% of the oil continues through the refrigeration circuit until it becomes dissolved in the liquid refrigerant in the flooded evaporator. The dissolved oil accumulates in the evaporator which not only starves the compressor of needed oil, but also affects the heat exchange function of the evaporator.